Brain structure & functionFeb 20, 2014

Daily rhythms of clock genes in rat brain fluid tissue vary by sex

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 27, 2026

Abstract

A 24-hour rhythm in the expression of the genes Per2 and Cry2 was observed in both male and female rat choroid plexus.

Circadian expression of Bmal1 and Per1 varied throughout the day, but this was only noted in females.
No significant differences in the expression of Bmal1, Clock, and Per1 were found in male choroid plexus.
Cultured choroid plexus cells exhibited significant circadian rhythms in the mRNA levels of Bmal1, Clock, and Per2.
The findings suggest that hormonal influences may regulate circadian rhythms in the choroid plexus, with differences observed between genders.

Simplified

It is well-documented that circadian rhythms are controlled by the circadian master clock of the mammalian brain, located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN clockwork is a cell autonomous mechanism consisting of a series of interlocked transcriptional/post-translational feedback loops. In turn, the SCN controls the seasonal rhythmicity of various biological processes, in particular the secretion pattern of hormones. Although the effects of gonadal hormones on circadian rhythmicity are clearly established, how the SCN integrates and regulates these hormonal stimuli remains unknown. We have previously found that clock genes are expressed in the choroid plexus (CP). Therefore, we compared the circadian expression of these genes in female and male rat CP. We show that there is a 24-h rhythm in the expression of Per2 and Cry2 in males and females. Bmal1 and Per1 expression also varied along the day, but only in females. Bmal1, Clock and Per1 mRNA did not show any significant differences in the CP of males. Moreover, data from cultured CP cells collected at different timepoints revealed significant circadian rhythms in mRNA abundance of Bmal1, Clock and Per2. In conclusion, our data show that the rat CP expresses all canonical clock genes and that their circadian expression differs between genders suggesting that hormones can regulate circadian rhythmicity in CP.

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Daily rhythms of clock genes in rat brain fluid tissue vary by sex

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